src/streamlit_app.py

# streamlit_app.py  — ENV-ONLY CONFIG (no st.secrets)
import os, io, pathlib, urllib.request
import numpy as np
import streamlit as st
from PIL import Image
from matplotlib import cm

# ---- import Detector from app/ or src/ ----
Detector, _last_err = None, None
for mod in ["app.inference_wav2vec", "app.inference",
            "src.inference_wav2vec", "src.inference"]:
    try:
        Detector = __import__(mod, fromlist=["Detector"]).Detector
        break
    except Exception as e:
        _last_err = e
if Detector is None:
    st.error(f"Could not import Detector from app/ or src/. Last error: {_last_err}")
    st.stop()

# ---- weights handling (ENV ONLY) ----
def cfg(name: str, default: str = "") -> str:
    v = os.getenv(name)
    return v if v not in (None, "") else default

def ensure_weights() -> str:
    wp  = cfg("MODEL_WEIGHTS_PATH", "app/models/weights/wav2vec2_classifier.pth")
    url = cfg("MODEL_WEIGHTS_URL", "")
    dest = pathlib.Path(wp)
    if not dest.exists() and url:
        dest.parent.mkdir(parents=True, exist_ok=True)
        with st.spinner(f"Downloading model weights to {dest} …"):
            urllib.request.urlretrieve(url, str(dest))
            st.toast("Weights downloaded", icon="✅")
    if not dest.exists() and not url:
        st.warning(
            f"Model weights not found at '{wp}'. "
            "Upload the .pth there OR set MODEL_WEIGHTS_URL in Settings → Variables & secrets."
        )
    return str(dest)

@st.cache_resource(show_spinner=True)
def load_detector():
    return Detector(weights_path=ensure_weights())

det = load_detector()

# ---- helpers ----
def cam_to_png_bytes(cam: np.ndarray) -> bytes:
    cam = np.asarray(cam, dtype=np.float32)
    cam = np.nan_to_num(cam, nan=0.0); cam = np.clip(cam, 0.0, 1.0)
    rgb = (cm.magma(cam)[..., :3] * 255).astype(np.uint8)
    buf = io.BytesIO(); Image.fromarray(rgb).save(buf, "PNG")
    return buf.getvalue()

def analyze(wav_bytes: bytes, source_hint: str):
    proba = det.predict_proba(wav_bytes, source_hint=source_hint)
    exp   = det.explain(wav_bytes, source_hint=source_hint)
    return proba, exp

# ---- UI ----
st.set_page_config(page_title="Voice Guard", page_icon="🛡️", layout="wide")
st.title("🛡️ Voice Guard — Human vs AI Speech")

left, right = st.columns([1,2], gap="large")
with left:
    st.subheader("Input")
    tab_rec, tab_up = st.tabs(["🎙️ Microphone", "📁 Upload"])
    wav_bytes, source_hint = None, None

    with tab_rec:
        st.caption("Record ~3–7 s. If mic fails, use Upload.")
        try:
            from audio_recorder_streamlit import audio_recorder
            audio = audio_recorder(text="Record", recording_color="#ff6a00",
                                   neutral_color="#2b2b2b", icon_size="2x")
            if audio:
                wav_bytes, source_hint = audio, "microphone"
                st.audio(wav_bytes, format="audio/wav")
        except Exception:
            st.info("Recorder not available—use Upload tab.")

    with tab_up:
        f = st.file_uploader("Upload wav/mp3/m4a/aac", type=["wav","mp3","m4a","aac"])
        if f:
            wav_bytes, source_hint = f.read(), "upload"
            st.audio(wav_bytes)

    st.markdown("---")
    run = st.button("🔍 Analyze", type="primary", use_container_width=True,
                    disabled=wav_bytes is None)

with right:
    st.subheader("Results")
    if run and wav_bytes:
        try:
            with st.spinner("Analyzing…"):
                proba, exp = analyze(wav_bytes, source_hint or "auto")
            ph = float(proba.get("human",0.0)); pa = float(proba.get("ai",0.0))
            label = (proba.get("label","human") or "human").upper()
            thr = float(proba.get("threshold",0.5))
            rule = proba.get("decision","threshold")
            thr_src = proba.get("threshold_source","—")
            rscore = proba.get("replay_score", None)

            c1,c2,c3 = st.columns(3)
            with c1: st.metric("Human", f"{ph*100:.1f}%")
            with c2: st.metric("AI", f"{pa*100:.1f}%")
            with c3:
                color = "#22c55e" if label=="HUMAN" else "#fb7185"
                st.markdown(f"**Final Label:** <span style='color:{color}'>{label}</span>", unsafe_allow_html=True)
                st.caption(f"thr({thr_src})={thr:.2f} • rule={rule} • replay={'—' if rscore is None else f'{float(rscore):.2f}'}")

            st.markdown("##### Explanation Heatmap")
            cam = np.asarray(exp.get("cam"), dtype=np.float32)
            st.image(cam_to_png_bytes(cam), caption="Spectrogram importance", use_column_width=True)

            with st.expander("Raw JSON (debug)"):
                st.json({"proba": proba, "explain": {"cam_shape": list(cam.shape)}})
        except Exception as e:
            st.error(f"Analyze failed: {e}")

st.caption("Upload 3–7s clips for the most reliable experience across browsers.")